You will learn in 8.02 that if you have a charged body changing direction, that constitutes an acceleration.
你们将在8。02中学到,如果一个带电体改变方向时,产生一个加速度。
You cannot have a spring pulled only at one side, because then it will then accelerate with infinite acceleration in that direction.
你不可能对弹簧只施加一边的拉力,因为那样的话弹簧就会以无穷大的加速度加速,就在这个方向上
And, you know acceleration means either change of speed or change of direction.
你知道加速度意味着,不是改变速度就是改变方向。
This particle is constantly changing its direction, but it therefore has an acceleration and the acceleration, we have shown here, is pointing towards the center.
这个质点恒定地改变它的运动方向,因此它具有加速度,而且这个加速度,我们前面也讲过了,指向圆心
Then you guys know, you just told me, acceleration is -9.8, We call it "minus" because it's accelerating down and up was taken to be the positive direction.
然后你们都知道,你告诉我,加速度是-9.8,我们取负号是因为加速度方向朝下,而正方向为竖直向上
This is the acceleration directed toward the center.
加速度方向指向圆心
It tells you when a particle moves in a circle, it has an acceleration in a negative R direction, namely directed towards the center.
它告诉你当一个物体在圆周上运动时,它有一个在 -R 方向的加速度,也就是说是直接指向圆心的
Whenever you see a particle moving in a circle, even if it's at a constant speed, it has an acceleration, v square over r directed towards the center.
只要看到质点做圆周运动,即使是匀速圆周运动,也存在一个加速度,大小为 v^2 / r,方向指向圆心
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